Ladders, scaffolds and similar devices are used extensively on construction sites, as well as in buildings. Especially in outdoor locations, the ground upon which the ladders and scaffolds are used very frequently is uneven, while it is necessary to have similar support for both legs of a ladder, as well as all of the legs of a scaffold. Many efforts have been made in the past to supply adjustable devices of various kinds for use in relation to ladders, as well as scaffolds, for purposes of enabling both legs of a ladder, and preferably all the uprights or legs of a scaffold, to be disposed upon firm support, even though the load-bearing surface is of an uneven nature.
The following patents disclose examples of adjustable supports for the legs of a ladder in order that both legs might be firmly positioned upon an otherwise uneven surface:
______________________________________ U.S. Pat. No. 898,973 - Curran 1908 U.S. Pat. No. 971,997 - Henning 1910 U.S. Pat. No. 1,197,727 - Finkle 1916 U.S. Pat. No. 3,021,921 - Poelvoorde et al 1962 U.S. Pat. No. 4,029,174 - Planck et al 1977 ______________________________________
Patents pertaining to scaffolds to adapt them to uneven surfaces:
______________________________________ U.S. Pat. No. 2,203,114 - Uecker et al 1940 U.S. Pat. No. 2,618,496 - Johnson 1952 U.S. Pat. No. 3,697,032 - Pearce 1972 ______________________________________
It will be seen from the foregoing patents that various means have been resorted to to effect adjustment of the lower ends of the legs of a ladder and uprights of a scaffold, some of these involving various types of threaded arrangements, while others, for example, utilize ratchet means of different types. Some of these are quick-acting, while others require somewhat time-consuming threaded adjusting means. The present invention provides improvements over the above-referred to adjustable mechanisms embodied in the foregoing listed patents, as well as many other patents which were considered, but from which the foregoing were selected as being representative.